Leaking Coolant Help?

Hi all. I haven't been using my Hi-Jet 97 1.0l Bus regularly last few weeks. Maybe doing 4miles in the week. What I've noticed is its not firing on all 3 pots when starting from cold. So with my foot gently on pedal its starts running smooth after 10secs, sometimes with the usual white smoke out of back of exhaust, until it gets hot. What I cant work out is what smells like coolant running like a tap on to floor from back of rad. Before I can get under to check it stops after around 10secs. Engine warms up and pressure builds up in Rad as normal. No leaks runs as it should. It doesn't happen when used regularly. Am I right in thinking it may be water in the exhaust from not being used regularly?
Any suggestions would be appreciated
Thanks